Silicon semiconductor processing has evolved sophisticated operations for fabricating integrated circuits. As advancement in fabrication process technology continues, the core and input/output (I/O) operating voltages of integrated circuits have decreased. However, operating voltages of auxiliary devices have remained about the same. The auxiliary devices include devices interfaced to the integrated circuits. Examples of the auxiliary devices include printers, scanners, disk drives, tape drives, microphones, speakers, or cameras.
An integrated circuit can include an interconnected array of active and passive elements, such as transistors, resistors, capacitors, and inductors, integrated with or formed on a substrate by a series of compatible processes. The auxiliary devices may operate at voltages above a breakdown voltage of the transistors contained within the integrated circuit. As the operating voltages applied to the transistors increase, the transistors will eventually breakdown allowing an uncontrollable increase in current. Examples of the detrimental effects of breakdown include punch-through, avalanche breakdown, and gate oxide breakdown to provide some examples. Furthermore, operating above the breakdown voltage for a significant duration reduces the lifetime of the transistors.
The isolation breakdown voltage may be limited by Nwell-Pwell junction breakdown voltage, which is typically less than 12-15 volts for an advanced CMOS process. Low voltage laterally diffused MOS (LDMOS) used with drain supply voltage (VDD) less than Nwell-Pwell breakdown or MOS devices for some analog applications (e.g., power management unit (PMU)) can be implemented into a system-on-chip (SOC). Fuse circuits operate within less than 6-8V and can be safely isolated by PN junctions. Conventional CMOS devices can be in the low to medium voltage domain, for which the standard junction isolation can be used for the device isolation.